Hard facing



United States Patent 3,109,917 HARD FACENG Alfred Schmidt and Erich Nonninger, Kapfenberg, Styria,

Austria, asslgnors to Gebr. Bohler Co. Alrtiengeselh scbar't, Vienna, Austria No Drawing. Filed Apr. 11, 1960, tier. No. 21,12553 Claims priority, application Austria Apr. 18, 1959 2 Claims. (Cl. 219-76) it has been wellknown, that cemented carbides can be welded in inert-gas-atmosphere either with or without admixes of auxiliary metals; this process has proved especially successful in bu-ilt-up-welding for making tools with cutting-edges. In this process also rods, containing cemented-carbides can be used as admixes.

As far as preparing of wear-resistant surfaces is concerned, this method only could be applied for relatively small surfaces, :i.e. surfaces of but a few square-cm., armor-platings on greater surfaces being sensible towards crack-formation and being likely to chip off if exposed to impact-stresses.

This invention deals with an improvement of that wellknown process, enabling armor-plating of greater surfaces, especially of round pieces entirely homogeneously, without any crack-formation involved.

Experiments have shown, that the auxiliary metal used for preparing *admixes of sintered-carbides is very important. The auxiliary metal used for those admixes is supposed to contain 5100% Ni, 0-95% Fe and/or 030% Cr.

Thus this invention relates to a process of preparing hard and wear-resistant surfaces by built-up-arc-welding in inert gas-atmospheres, whereas admixes of sintered carbides are used, which primarily consists of tungstencarbides which may be combined with other cemented carbides and of 5-30% auxiliary metal; this process is characterized by the fact, that the auxiliary metal used for armor-plating great surfaces, which are sensible to wards crack-formation, especially for armor-plating round pieces, consists of 5100% Ni, 0-95% Fe and/or 030% Cr, besides unavoidable impurities.

lBesides tungsten-carbide, which is supposed to be the main component, its percentage being supposed to exceed 50%, carbides of molybdenum, chromium, tantalum, niobium, titanium, zirconium and similar can also be used.

The auxiliary metal either can be pure nickel-powder or nickel-powder mixed with powdered iron or chromium; this auxiliary metal is added to the powdered mixture, which is to be sintered and to be pressed for preparing the admix.

Powdered austenitic Cr-Ni-steel, however, also can be applied as auxiliary metal.

Admixes preferably are made in the usual manner: the powdered mixture, consisting of cemented carbides and binding-metal is mixed with an organic binding-agreant, such as synthetic resin; this mixture is extruded to rods, which subsequently are sintered at temperatures ranging between 900 and 1300 C.

Welding-rods consisting of 85% WC and 15% Ni for 3, l 00,9 i Patented Nov. 5, l 963 ice instance have been used for armor-plating rings for wirerod-guides according to the process suggested by this invention. No wear could be observed on those rings after 478 hours running-time. However rings, armorplated with hardened punching-tool-steel, containing 13% chromium and 2% carbon already have become completely worn out and therefore unable for use, after 334 hours if exposed to the same amount of stress.

it cobalt and/or iron are used as binding-metals the resistance towards wear will be presumably reduced by at least 20% under comparable conditions.

If admixes as suggested by this invention are used for welding in inert atmospheres, hardnesses ranging between 64 and 67 Rockwell-units are achieved. The favourable effect of binding-metals added to those admixes evidently is due to formation of a viscous transition-Zone between the admix and the basic material. This enables continuous building up of thicker layers without any crack-formation involved during argon arc-welding. Those layers can have thicknesses ranging between 4 and 6 mm. It is also possible to apply several layers by built-up-welding without any crack-formation involved.

Those admixes as specified by the invention besides have proved especially advantageous owing to the fact, that in argon-arc -welding hardnesses ranging between 64 and 67 RC immediately can be achieved, whereas hardnesses of about 52 RC only are achieved, with the same weldingprocess, if sintered carbides, such as WC is used with Co and/ or F e as binding-metal.

What we claim is:

1. A process of hard facing by shielded arc welding employing a hard facing sintered rod produced by molding and sintering at a temperature of 900-1300 C. an admixture of powdered materials comprising a major portion of hard metal carbides and 5% to 30% of a cobalt free alloy consisting essentially of a metal selected from the group consisting of nickel, iron and chromium and mixtures thereof, at least 5% nickel being present in the alloy and less than 30% chromium being present in the alloy and an organic synthetic resin as a binding agent.

2. The process of claim 1 wherein the hard metal carbide is tungsten carbide.

References Cited in the file of this patent UNITED STATES PATEb TS 1,721,416 Schroter July 16, 1929 1,977,361 laylor et al Oct. 16, 1934 2,002,198 Wissler May 21, 1935 2,067,166 Ealke June 12, 1937 2,137,471 Zublin Nov. 22, 1938 2,219,462 Wissler Oct. 29, 1940 2,507,195 Colbeck et al May 9, 1950 2,847,555 Yenni Aug. 12, 1958 2,982,845 Yenni et a]. May 2, 1961 2,998,922 Gibson Sept. 5, 1961 FOREIGN PATENTS 395,721 Great Britain July 7, 1933 592,214 Canada Feb. 9, 1960 732,440 Great Britain June 22, 1955 

1. A PROCESS OF HARD FACING BY SHIELDED ARC WELDING EMPLOYING A HARD FACING SINTERED ROD PRODUCED BY MOLDING AND SINTERING AT A TEMPERATURE OF 900-1300*C. AN ADMIXTURE OF POWDERED MATERIALS COMPRISING A MAJOR PORTION OF HARD METAL CARBIDES AND 5% TO 30% OF A COBALT FREE ALLOY CONSISTING ESSENTIALLY OF A METAL SELECTED FROM THE GROUP CONSISTING OF NICKEL, IRON AND CHROMIUM AND MIXTURES THEREOF, AT LEAST 5% NICKEL BEING PRESENT INTHE ALLOY AND LESS THAN 30% CHROMIUM BEING PRESENT IN THE ALLOY AND AN ORGANIC SYNTHETIC RESIN AS A BINDING AGENT. 